JP2003251198A - Ceramic honeycomb structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the destruction of a ceramic honeycomb structure generated in the diagonal direction of cells by a heat shock or heat stress generated when the ceramic honeycomb structure is used as a catalyst converter or a fine particle collection filter. <P>SOLUTION: In the ceramic honeycomb structure having an outer peripheral wall and a large number of the cells surrounded by cell walls on the inner peripheral side of the outer peripheral wall, the cell wall thicknesses of different cell walls are not uniform, and the average value t<SB>av</SB>of the cell wall thicknesses and the maximum value t<SB>max</SB>and minimum value t<SB>min</SB>of the cell wall thicknesses satisfy the relation of t<SB>av</SB>/(t<SB>max</SB>-t<SB>min</SB>)≤40. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic honeycomb structure suitable for use as a carrier for an exhaust gas purifying catalyst for an automobile engine or as a filter for removing fine particles in exhaust gas of a diesel engine. is there.

[0002]

2. Description of the Related Art In order to meet the demand for reduction of harmful substances contained in exhaust gas emitted from engines such as automobiles from the viewpoint of preservation of local environment and global environment, a carrier for a catalytic converter for purifying exhaust gas. A ceramic honeycomb structure is used as a filter for collecting fine particles. The cell structure of this ceramic honeycomb structure has a quadrangular cell shape, particularly a square cell shape as shown in FIG. 3 because it is suitable for reducing pressure loss and is easy to manufacture. It is generally uniform within the structure. Therefore, the strength is high in the direction parallel to the cell wall, but the strength is low in the direction oblique to the cell wall. Therefore, the conventional honeycomb structure may be destroyed in the diagonal direction of the cell due to thermal shock or thermal stress generated when it is used as a catalytic converter or a filter for collecting fine particles. For example, FIG. 4 shows a schematic view of a specific state of destruction in a conventional ceramic honeycomb structure. In order to solve such a defect, Japanese Patent Application Laid-Open No. Sho 5
In JP-A 5-147154, the strength of the honeycomb structure outer peripheral side is improved by making the thickness of the cell wall near the outer periphery thicker than that of the inner cell wall, and as a result, the strength of the entire honeycomb structure is improved. Is disclosed. Further, Japanese Patent Publication No. 51-20435 discloses a manufacturing method for forming an enlarging portion such as an arc shape or a straight shape at the intersection of the cell walls, which is a drawback of the prior art. It is said that it is possible to solve the problems of crack generation due to stress concentration on a portion and deterioration of catalytic reaction efficiency due to poor exhaust gas flow near the corners.

[0003]

However, even in the above-mentioned prior art, there is a problem in that the cells are broken in the diagonal direction of the cell due to thermal shock or thermal stress generated when they are used as a catalytic converter or a filter for collecting particulates. It has not been resolved. For example, Japanese Patent Laid-Open No. 55-1471
In Japanese Patent Laid-Open No. 54-54, although the thickness of the cell wall near the outer circumference is increased to improve the strength near the outer circumference, the cell wall of the same thickness is formed near the center, so The strength is the same in various places near the center of the honeycomb structure, when thermal shock or thermal stress occurs, stress concentration occurs at the cell wall intersections, and cracks propagate in a chain at adjacent cell wall intersections. There was a problem of destruction in the diagonal direction of the cell. In addition, in Japanese Patent Publication No. 51-20435,
An arcuate or straight line is formed at the intersection of the cell walls to reduce stress concentration at the intersections of the cell walls, but the strength of the intersections of the cell walls is the same at various points in the honeycomb structure. When a thermal shock or thermal stress occurs,
There is a problem that cracks propagate in a chain at adjacent cell wall intersections and are broken in the diagonal direction of the cells.

The present invention has been made in view of the above problems, and cracks propagate in a diagonal direction of cells at cell cell intersections where stress concentration occurs even when thermal shock or thermal stress occurs. An object of the present invention is to provide a ceramic honeycomb structure capable of preventing the phenomenon of breakage. That is, it is intended to obtain a ceramic honeycomb structure having excellent thermal shock resistance.

[0005]

The first invention of the present invention is as follows:
In a ceramic honeycomb structure having an outer peripheral wall and a large number of cells surrounded by cell walls on the inner peripheral side of the outer peripheral wall, the cell wall thickness of at least some of the cells is not uniform. It is a ceramic honeycomb structure. The second invention of the present invention is that the average value t _av of the cell wall thickness and the maximum value t _max and the minimum value t of the cell wall thickness.
_min is a ceramic honeycomb structure characterized by satisfying a relationship of t _av / (t _max −t _min ) ≦ 40.

Next, the reason for the configuration of the present invention will be described. In the configuration of the first aspect of the present invention, the cell wall thickness of the cell walls in the ceramic honeycomb structure is not uniform. Here, that the cell wall thickness is not uniform means that at least the cell wall thickness is different when viewed in a cross section perpendicular to the axial direction. For example, this may be the case where some of the cell walls forming the same cell of the honeycomb structure are different from each other, the cell wall thicknesses are different between adjacent cells, the parallel cell wall thicknesses are different from each other, and the like. Therefore, since the thickness of the partition wall is not uniform, the cell wall thickness forming the cell wall intersection varies from cell to cell. Therefore, the strength of the cell wall intersection varies from cell to cell,
Since it does not become constant at various points in the honeycomb structure, cell wall intersections having the same strength do not exist continuously, and when thermal stress occurs, a crack develops in a chain at the cell wall intersections, It is possible to prevent the phenomenon that the cells are broken in the diagonal direction, and as a result, excellent thermal shock resistance characteristics are obtained. Furthermore, in the configuration of the second aspect of the present invention, the cell wall thickness is the average value t _av of the cell wall,
The maximum value t _max and the minimum value t _{min of the} cell wall thickness satisfy the relationship of t _av / (t _max −t _min ) ≦ 40. Where t _av / (t _max −t
The value of ( _min ) indicates the degree of variation with respect to the average value of the cell wall thickness, and the variation of the cell wall thickness is t
_By setting the value of _av / (t _max −t _min ) to be 40 or less, the cell wall thickness in the honeycomb structure is not uniform, so that there is no continuous cell wall intersection having so-called similar strength. Therefore, it is possible to prevent the phenomenon that cracks develop in a chain at the cell wall intersections due to thermal shock or thermal stress and break in the diagonal direction of the cell,
As a result, excellent thermal shock resistance characteristics can be obtained. On the other _hand, if the value of _{t a v / (t max -t} min) is more than 40, since the cell wall thickness of the honeycomb structure difference is reduced, since the strength of the cell wall intersections converges to the same extent The reason for this is that thermal shock and thermal stress cause a chain of cracks to develop at the intersections of the cell walls, which makes it easier to break in the diagonal direction of the cell, and the thermal shock resistance deteriorates. t _av / (t _max
The value of −t _min ) is preferably 1 to 40, more preferably 2 to 30. Where t _av / (t _max
The preferable range of the value of −t _min ) is set to 1 or more is that
If it is less than 1, the difference between the minimum wall thickness and the maximum wall thickness becomes large. Therefore, during extrusion molding of a honeycomb structure, the velocity balance of the clay clay of the ceramic raw material discharged from the slit portion of the known extrusion die. May deteriorate and the molded article may be bent or cracked, which is not preferable. By forming a curved portion as shown in FIG. 2 (c) at the intersection of the cell walls, the stress concentration factor at the intersection of the cell walls can be reduced, so that the strength at the intersection of the cell walls is improved and cracks are generated. It is possible to further prevent the phenomenon that the cells are broken in the diagonal direction. As the ceramic material constituting the ceramic honeycomb structure of the present invention, the present invention is mainly used as a carrier for a catalyst for purifying exhaust gas of an automobile engine or as a filter for removing fine particles in exhaust gas of a diesel engine. Since it is used, it is preferable to use a material having excellent heat resistance, cordierite, alumina,
It is preferable to use a ceramic material containing at least one selected from the group consisting of mullite, silicon nitride, silicon carbide and LAS as a main crystal. Among them, the ceramic honeycomb structure having cordierite as a main crystal is most preferable because it is inexpensive, has excellent heat resistance and chemical resistance, and has low thermal expansion.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in detail based on Examples.

Example 1 A ceramic honeycomb structure of the present invention comprises a cordierite forming raw material powder such as kaolin, calcined kaolin, alumina, aluminum hydroxide, silica and talc.
It is prepared as a raw material by mixing so as to have a cordierite composition. To this, a binder, a molding aid such as a lubricant, and if necessary, a pore-forming agent is added and mixed, and then water is added and kneaded,
A plasticizable batch was prepared and a honeycomb molded body was obtained by extrusion molding. At this time, the groove width on the outlet side of the known extrusion mold is adjusted so that the cell wall thickness of at least a part of the cells of the honeycomb structure becomes non-uniform, and the cell as shown in FIG. It was a molded product having a wall. Then, the obtained compact was fired at 1400 ° C. to obtain a cordierite ceramic honeycomb structure 10 shown in FIG. The honeycomb structure has an outer diameter of 267 mm and a length of 30.
The cell wall thickness was 0 mm, the average cell wall thickness was 0.3 mm, and the cell number was 46.5 cells / cm ² . The porosity of the honeycomb structure is 6
5% and the average pore diameter was 20 μm. The thickness of the cell wall of the obtained honeycomb structure was measured by the following method.
As shown in FIG. 5 (a), four cell walls surrounding the cell are divided into 5 locations × 5 locations in total at 25 locations where the diameters 14 and 13 of the X-axis and Y-axis of the honeycomb structure are divided at equal intervals. The thickness 15 of was measured. The measurement is performed using a projector with a magnification of 100 times, and as shown in FIG. 5B, the cell wall thickness 15 is measured at an intermediate point that divides the cell wall length into approximately two equal parts 16, The cell wall thickness was used. Thus four locations / 1 cell × 25 places were measured, the measured value of the cell wall thickness of a total of 100 points, _/ the average value _{t av,} the maximum value _{t ma x} and minimum value _{t min} from _t av _{(t max} The value of −t _min ) was determined. The thermal shock resistance of the obtained ceramic honeycomb structure was evaluated. The thermal shock resistance evaluation test was conducted by inserting the ceramic honeycomb structure into an electric furnace heated to a constant temperature, holding it for 30 minutes, then rapidly cooling it to room temperature, and then visually observing the temperature difference (heating temperature -Room temperature) was defined as the thermal shock resistance temperature. If no crack was found by visual inspection, the temperature was raised to 25 ° C. and the same test was performed, and the test was repeated until a crack was generated.
The number of tests was three, and the average was shown. The results are shown in Table 1. As shown in Table 1, the cell wall thickness is non-uniform in the honeycomb structure, t _av / (t _max −t).
_min. ) of 40 or less. 1-5 and test N
O. The honeycomb structure of Nos. 8 to 9 has a problem in that the thermal shock resistance is used when used as a carrier for a catalyst for purifying exhaust gas of an automobile engine or as a filter for removing fine particles in exhaust gas of a diesel engine. The thermal shock resistance was 700 ° C. or higher, which is a non-existent level. For this reason, there is little concern that cracks may occur due to thermal shock during actual use, leading to destruction. On the other hand, t _av / (t _max −t
_min. ) value exceeds 40. In the honeycomb structures of Nos. 6, 7 and 9, the difference in cell wall thickness is small and uniform, so that the thermal shock resistance temperature is less than 700 ° C., and cracks occur due to thermal shock during actual use and break. I'm worried.

[0008]

[Table 1]

[0009]

As described in detail above, according to the present invention, since the cell wall thickness of the cell wall in the ceramic honeycomb structure is not uniform, the strength of the cell wall intersection is constant at various points in the honeycomb structure. Since there are no continuous low-strength cell wall intersections, when a thermal shock or thermal stress occurs, cracks develop in a chain at the cell wall intersections and break in the diagonal direction of the cell. This phenomenon can be prevented, and a ceramic honeycomb structure having excellent thermal shock resistance can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a ceramic honeycomb structure according to an embodiment.

FIG. 2 (a) is a view showing cell walls of the ceramic honeycomb structure of the present invention. (B) It is a figure which shows the cell wall of another ceramic honeycomb structure of this invention. (C) It is a figure which shows the cell wall of another ceramic honeycomb structure of this invention.

FIG. 3 is a view showing cell walls of a conventional ceramic honeycomb structure.

[Fig. 4] Fig. 4 is a schematic view of a concrete destruction state in a conventional ceramic honeycomb structure.

FIG. 5 is a diagram showing measurement points of cell wall thickness of a ceramic honeycomb structure.

[Explanation of symbols]

10: Ceramic honeycomb structure 11: Cell wall 12: Through hole 13: Y-axis diameter 14: Diameter of X axis 15: Cell wall thickness 16: Bisection length of cell wall

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[Procedure amendment]

[Submission date] October 18, 2002 (2002.10.
18)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

[0005]

The first invention of the present invention is as follows:
In a ceramic honeycomb structure having an outer peripheral wall and a large number of cells surrounded by cell walls on the inner peripheral side of the outer peripheral wall, the cell wall thickness of the cells is the entire cross-sectional area perpendicular to the axial direction.
It is a ceramic honeycomb structure characterized by being not uniform in the region . The second invention of the present invention is the axial direction.
Divide the X-axis and Y-axis diameters in a section perpendicular to the direction into equal intervals
5 cells x 5 cells, total 25 cells,
The four surrounding cell wall thicknesses, and the average value t of the cell wall thicknesses
The maximum value t _max and the minimum value t of _av and the cell wall thickness
_The ceramic honeycomb structure according to claim 1, wherein _min satisfies the relationship of _tav / ( _tmax- tmin) ≤40.

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

Next, the reason for the configuration of the present invention will be described. In the configuration of the first aspect of the present invention, the cell wall thickness of the cell walls in the ceramic honeycomb structure is not uniform. Here, that the cell wall thickness is not uniform means that the cell wall thickness is different in the entire cross-sectional area when viewed in a cross section perpendicular to the axial direction. For example, this may be the case where some of the cell walls forming the same cell of the honeycomb structure are different from each other, the cell wall thicknesses are different between adjacent cells, the parallel cell wall thicknesses are different from each other, and the like. Therefore, since the thickness of the partition wall is not uniform, the cell wall thickness forming the cell wall intersection varies from cell to cell. For this reason, the strength of the cell wall intersection varies from cell to cell, and is not constant throughout the honeycomb structure.
Since there are no continuous cell wall intersections with the same strength, it is possible to prevent the phenomenon that cracks develop in a chain at the cell wall intersections when thermal stress occurs and the cells break in the diagonal direction of the cell. Therefore, excellent thermal shock resistance can be obtained as a result. Further, in the configuration of the second aspect of the present invention , the X-axis and the Y-axis in a cross section perpendicular to the axial direction are provided.
5 places that divide the diameter of the shaft into equal intervals x 5 places total 25 places
For each cell, the thickness of the four cell walls surrounding the cell is
As for the cell wall thickness, the average value t _av of the cell wall, the maximum value t _max and the minimum value t _{min of} the cell wall thickness satisfy the relationship of t _av / (t _max −t _min ) ≦ 40. There is. Where t _av / (t _max −t
The value of ( _min ) indicates the degree of variation with respect to the average value of the cell wall thickness, and the variation of the cell wall thickness is t
_By setting the value of _av / (t _max −t _min ) to be 40 or less, the cell wall thickness in the honeycomb structure is not uniform, so that there is no continuous cell wall intersection having so-called similar strength. Therefore, it is possible to prevent the phenomenon that cracks develop in a chain at the cell wall intersections due to thermal shock or thermal stress and break in the diagonal direction of the cell,
As a result, excellent thermal shock resistance characteristics can be obtained. On the other _hand, if the value of _{t a v / (t max -t} min) is more than 40, since the cell wall thickness of the honeycomb structure difference is reduced, since the strength of the cell wall intersections converges to the same extent The reason for this is that thermal shock and thermal stress cause a chain of cracks to develop at the intersections of the cell walls, which makes it easier to break in the diagonal direction of the cell, and the thermal shock resistance deteriorates. t _av / (t _max
The value of −t _min ) is preferably 1 to 40, more preferably 2 to 30. Where t _av / (t _max
The preferable range of the value of −t _min ) is set to 1 or more is that
If it is less than 1, the difference between the minimum wall thickness and the maximum wall thickness becomes large. Therefore, during extrusion molding of a honeycomb structure, the velocity balance of the clay clay of the ceramic raw material discharged from the slit portion of the known extrusion die. May deteriorate and the molded article may be bent or cracked, which is not preferable. By forming a curved portion as shown in FIG. 2 (c) at the intersection of the cell walls, the stress concentration factor at the intersection of the cell walls can be reduced, so that the strength at the intersection of the cell walls is improved and cracks are generated. It is possible to further prevent the phenomenon that the cells are broken in the diagonal direction. As the ceramic material constituting the ceramic honeycomb structure of the present invention, the present invention is mainly used as a carrier for a catalyst for purifying exhaust gas of an automobile engine or as a filter for removing fine particles in exhaust gas of a diesel engine. Since it is used, it is preferable to use a material having excellent heat resistance, cordierite, alumina,
It is preferable to use a ceramic material containing at least one selected from the group consisting of mullite, silicon nitride, silicon carbide and LAS as a main crystal. Among them, the ceramic honeycomb structure having cordierite as a main crystal is most preferable because it is inexpensive, has excellent heat resistance and chemical resistance, and has low thermal expansion.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in detail based on Examples.

Example 1 A ceramic honeycomb structure of the present invention comprises a cordierite forming raw material powder such as kaolin, calcined kaolin, alumina, aluminum hydroxide, silica and talc.
It is prepared as a raw material by mixing so as to have a cordierite composition. To this, a binder, a molding aid such as a lubricant, and if necessary, a pore-forming agent is added and mixed, and then water is added and kneaded,
A plasticizable batch was prepared and a honeycomb molded body was obtained by extrusion molding. At this time, the cell wall thickness of the honeycomb structure
The molding groove width on the outlet side of a known extrusion molding die was adjusted so that the above-mentioned was non-uniform over the entire cross-sectional area perpendicular to the axial direction to obtain a molded body having a cell wall as shown in FIG. Then, the obtained compact was fired at 1400 ° C. to obtain a cordierite ceramic honeycomb structure 10 shown in FIG. The outer diameter of the honeycomb structure is 267 m.
m, the length was 300 mm, the average cell wall thickness was 0.3 mm, and the number of cells was 46.5 cells / cm ² . The porosity of the honeycomb structure was 65%, and the average pore diameter was 20 μm.
The thickness of the cell wall of the obtained honeycomb structure was measured by the following method. As shown in FIG. 5 (a), four cell walls surrounding the cell are divided into 5 locations × 5 locations in total at 25 locations where the diameters 14 and 13 of the X-axis and Y-axis of the honeycomb structure are divided at equal intervals. The thickness 15 of was measured. Measurement is 1 magnification
The cell wall thickness 15 at the midpoint at which the length of the cell wall is divided into two approximately 16 is measured as shown in FIG. did. The average value t _av and the maximum value t are obtained from the measured cell wall thicknesses at 100 points in total at 4 points / one cell × 25 points thus measured.
_{ma x} and minimum value _{t min} from _t av _{/ (t} max -t
_min ) was obtained. The thermal shock resistance of the obtained ceramic honeycomb structure was evaluated. The thermal shock resistance evaluation test was conducted by inserting the ceramic honeycomb structure into an electric furnace heated to a constant temperature, holding it for 30 minutes, then rapidly cooling it to room temperature, and then visually observing the temperature difference (heating temperature -Room temperature) was defined as the thermal shock resistance temperature. If no crack was found by visual inspection, the temperature was raised to 25 ° C. and the same test was performed, and the test was repeated until a crack was generated. The number of tests was three, and the average was shown. The results are shown in Table 1. As shown in Table 1,
The cell wall thickness is non-uniform in the honeycomb structure t _av /
Test No. with a value of (t _max −t _min ) of 40 or less. 1
~ 5 and test NO. The honeycomb structure of Nos. 8 to 9 has a thermal shock resistance when used as a carrier for a catalyst for purifying exhaust gas of an automobile engine or as a filter for removing fine particles in exhaust gas of a diesel engine,
The thermal shock resistance was 700 ° C or higher, which was a level without problems. For this reason, there is little concern that cracks may occur due to thermal shock during actual use, leading to destruction. On the other hand, t _av / (t
Test NO value exceeds 40 _max -t _min). 6,
In the honeycomb structures 7 and 9, the difference in cell wall thickness is small and uniform, so the thermal shock resistance temperature is less than 700 ° C., and there is a risk of cracking due to thermal shock during actual use and destruction. is there. ─────────────────────────────────────────────────── ───

[Procedure amendment]

[Submission date] January 10, 2003 (2003.1.1
0)

[Procedure Amendment 1]

[Document name to be amended] Statement

[Name of item to be amended] Claims

[Correction method] Change

[Correction content]

[Claims]

[Procedure Amendment 2]

[Document name to be amended] Statement

[Name of item to be corrected] 0005

[Correction method] Change

[Correction content]

[0005]

The first invention of the present invention is as follows:
In a ceramic honeycomb structure having an outer peripheral wall and a large number of cells surrounded by cell walls on the inner peripheral side of the outer peripheral wall, in at least some of the cells, the cell wall
Cell wall thickness that does not have uniform thickness and constitutes cell wall intersections
Is different for each cell, which is a ceramic honeycomb structure. In addition, the second invention of the present invention is a total of 25 locations of 5 locations × 5 locations that divide the diameters of the X-axis and the Y-axis in a cross section perpendicular to the axial direction at equal intervals. Wall thickness, the average value of the cell wall thickness t _av
And the maximum value t _max and the minimum value t _{min of the} cell wall thickness satisfy the relationship of t _av / (t _max −t _min ) ≦ 40, The ceramic honeycomb structure according to claim 1. .

[Procedure 3]

[Document name to be amended] Statement

[Correction target item name] 0006

[Correction method] Change

[Correction content]

Next, the reason for the configuration of the present invention will be described. In the configuration of the first aspect of the present invention, the cell wall thickness of the cell walls in the ceramic honeycomb structure is not uniform. Here, that the cell wall thickness is not uniform means that at least the cell wall thickness is different when viewed in a cross section perpendicular to the axial direction. For example, this may be the case where some of the cell walls forming the same cell of the honeycomb structure are different from each other, the cell wall thicknesses are different between adjacent cells, the parallel cell wall thicknesses are different from each other, and the like. Therefore, since the thickness of the partition wall is not uniform, the cell wall thickness forming the cell wall intersection varies from cell to cell. Therefore, the strength of the cell wall intersection varies from cell to cell,
Since it does not become constant at various points in the honeycomb structure, cell wall intersections having the same strength do not exist continuously, and when thermal stress occurs, a crack develops in a chain at the cell wall intersections, It is possible to prevent the phenomenon that the cells are broken in the diagonal direction, and as a result, excellent thermal shock resistance characteristics are obtained. Further, in the configuration of the second invention of the present invention, the cell is surrounded by 5 cells × 5 cells at a total of 25 cells that divide the diameters of the X axis and the Y axis in a cross section perpendicular to the axial direction at equal intervals. The cell wall thickness is the average value t _av of the cell wall, and the maximum value t _max and the minimum value t _{min of} the cell wall thickness are t _av / (t _max −t _min ). The relationship of ≦ 40 is satisfied. Where t _av / (t _max −t
The value of ( _min ) indicates the degree of variation with respect to the average value of the cell wall thickness, and the variation of the cell wall thickness is t
_By setting the value of _av / (t _max −t _min ) to be 40 or less, the cell wall thickness in the honeycomb structure is not uniform, so that there is no continuous cell wall intersection having so-called similar strength. Therefore, it is possible to prevent the phenomenon that cracks develop in a chain at the cell wall intersections due to thermal shock or thermal stress and break in the diagonal direction of the cell,
As a result, excellent thermal shock resistance characteristics can be obtained. On the other _hand, if the value of _{t a v / (t max -t} min) is more than 40, since the cell wall thickness of the honeycomb structure difference is reduced, since the strength of the cell wall intersections converges to the same extent The reason for this is that thermal shock and thermal stress cause a chain of cracks to develop at the intersections of the cell walls, which makes it easier to break in the diagonal direction of the cell, and the thermal shock resistance deteriorates. t _av / (t _max
The value of −t _min ) is preferably 1 to 40, more preferably 2 to 30. Where t _av / (t _max
The preferable range of the value of −t _min ) is set to 1 or more is that
If it is less than 1, the difference between the minimum wall thickness and the maximum wall thickness becomes large. Therefore, during extrusion molding of a honeycomb structure, the velocity balance of the clay clay of the ceramic raw material discharged from the slit portion of the known extrusion die. May deteriorate and the molded article may be bent or cracked, which is not preferable. By forming a curved portion as shown in FIG. 2 (c) at the intersection of the cell walls, the stress concentration factor at the intersection of the cell walls can be reduced, so that the strength at the intersection of the cell walls is improved and cracks are generated. It is possible to further prevent the phenomenon that the cells are broken in the diagonal direction. As the ceramic material constituting the ceramic honeycomb structure of the present invention, the present invention is mainly used as a carrier for a catalyst for purifying exhaust gas of an automobile engine or as a filter for removing fine particles in exhaust gas of a diesel engine. Since it is used, it is preferable to use a material having excellent heat resistance, cordierite, alumina,
It is preferable to use a ceramic material containing at least one selected from the group consisting of mullite, silicon nitride, silicon carbide and LAS as a main crystal. Among them, the ceramic honeycomb structure having cordierite as a main crystal is most preferable because it is inexpensive, has excellent heat resistance and chemical resistance, and has low thermal expansion.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0007

[Correction method] Change

[Correction content]

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in detail based on Examples.

Example 1 A ceramic honeycomb structure of the present invention comprises a cordierite forming raw material powder such as kaolin, calcined kaolin, alumina, aluminum hydroxide, silica and talc.
It is prepared as a raw material by mixing so as to have a cordierite composition. To this, a binder, a molding aid such as a lubricant, and if necessary, a pore-forming agent is added and mixed, and then water is added and kneaded,
A plasticizable batch was prepared and a honeycomb molded body was obtained by extrusion molding. At this time, at least the honeycomb structure
The molding groove width on the outlet side of a known extrusion molding die was adjusted so that the cell wall thickness of some cells became non-uniform, and a molded body having a cell wall as shown in FIG. 2 was obtained. Then, the obtained compact was fired at 1400 ° C. to obtain a cordierite ceramic honeycomb structure 10 shown in FIG. The honeycomb structure has an outer diameter of 267 mm and a length of 30.
The cell wall thickness was 0 mm, the average cell wall thickness was 0.3 mm, and the cell number was 46.5 cells / cm ² . The porosity of the honeycomb structure is 6
5% and the average pore diameter was 20 μm. The thickness of the cell wall of the obtained honeycomb structure was measured by the following method.
As shown in FIG. 5 (a), four cell walls surrounding the cell are divided into 5 locations × 5 locations in total at 25 locations where the diameters 14 and 13 of the X-axis and Y-axis of the honeycomb structure are divided at equal intervals. The thickness 15 of was measured. The measurement is performed using a projector with a magnification of 100 times, and as shown in FIG. 5B, the cell wall thickness 15 is measured at an intermediate point that divides the cell wall length into approximately two equal parts 16, The cell wall thickness was used. Thus four locations / 1 cell × 25 places were measured, the measured value of the cell wall thickness of a total of 100 points, _/ the average value _{t av,} the maximum value _{t ma x} and minimum value _{t min} from _t av _{(t max} The value of −t _min ) was determined. The thermal shock resistance of the obtained ceramic honeycomb structure was evaluated. The thermal shock resistance evaluation test was conducted by inserting the ceramic honeycomb structure into an electric furnace heated to a constant temperature, holding it for 30 minutes, then rapidly cooling it to room temperature, and then visually observing the temperature difference (heating temperature -Room temperature) was defined as the thermal shock resistance temperature. If no crack was found by visual inspection, the temperature was raised to 25 ° C. and the same test was performed, and the test was repeated until a crack was generated.
The number of tests was three, and the average was shown. The results are shown in Table 1. As shown in Table 1, the cell wall thickness is non-uniform in the honeycomb structure, t _av / (t _max −t).
_min. ) of 40 or less. 1-5 and test N
O. The honeycomb structure of Nos. 8 to 9 has a problem in that the thermal shock resistance is used when used as a carrier for a catalyst for purifying exhaust gas of an automobile engine or as a filter for removing fine particles in exhaust gas of a diesel engine. The thermal shock resistance was 700 ° C. or higher, which is a non-existent level. For this reason, there is little concern that cracks may occur due to thermal shock during actual use, leading to destruction. On the other hand, t _av / (t _max −t
_min. ) value exceeds 40. In the honeycomb structures of Nos. 6, 7 and 9, the difference in cell wall thickness is small and uniform, so that the thermal shock resistance temperature is less than 700 ° C., and cracks occur due to thermal shock during actual use and break. I'm worried.

[Procedure Amendment 5]

[Document name to be amended] Statement

[Name of item to be corrected] Brief description of the drawing

[Correction method] Change

[Correction content]

[Brief description of drawings]

FIG. 1 is a perspective view showing a ceramic honeycomb structure according to an embodiment.

FIG. 2 (a) is a view showing cell walls of the ceramic honeycomb structure of the present invention. (B) It is a figure which shows the cell wall of another ceramic honeycomb structure of this invention.

FIG. 3 is a view showing cell walls of a conventional ceramic honeycomb structure.

[Fig. 4] Fig. 4 is a schematic view of a concrete destruction state in a conventional ceramic honeycomb structure.

FIG. 5 is a diagram showing measurement points of cell wall thickness of a ceramic honeycomb structure.

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[Submission date] April 22, 2003 (2003.4.2)
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[Name of item to be amended] Claims

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[Claims]

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[Name of item to be corrected] 0005

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[0005]

The first invention of the present invention is as follows:
In a ceramic honeycomb structure having an outer peripheral wall and a large number of cells surrounded by cell walls on the inner peripheral side of the outer peripheral wall, the cell wall thicknesses of the cells are not uniform, and the cell wall forming a cell wall intersecting portion is formed. The ceramic honeycomb structure is characterized in that the thickness is different for each cell. In addition, the second invention of the present invention is a total of 25 locations of 5 locations × 5 locations that divide the diameters of the X-axis and the Y-axis in a cross section perpendicular to the axial direction at equal intervals. The wall thickness, the average value t _av of the cell wall thickness and the maximum value t _{max of} the cell wall thickness,
The ceramic honeycomb structure according to claim 1, wherein the minimum value t _min satisfies the relationship of t _av / (t _max −t _min ) ≦ 40.

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Next, the reason for the configuration of the present invention will be described. In the configuration of the first aspect of the present invention, the cell wall thickness of the cell walls in the ceramic honeycomb structure is not uniform. Here, the fact that the cell wall thickness is not uniform means that the cell wall thickness is different when viewed in a cross section perpendicular to the axial direction. For example, this may be the case where some of the cell walls forming the same cell of the honeycomb structure are different from each other, the cell wall thicknesses are different between adjacent cells, the parallel cell wall thicknesses are different from each other, and the like. Therefore, since the thickness of the partition wall is not uniform, the cell wall thickness forming the cell wall intersection varies from cell to cell. For this reason, the strength of the cell wall intersection differs from cell to cell and is not constant at various points in the honeycomb structure, so that there is no continuous cell wall intersection having the same strength, so thermal stress occurs. At this time, it is possible to prevent a phenomenon that cracks are propagated in a cell wall intersection portion in a chained manner and are broken in a diagonal direction of the cell, and as a result, excellent thermal shock resistance characteristics are obtained. Further, in the configuration of the second invention of the present invention, the cell is surrounded by 5 cells × 5 cells at a total of 25 cells that divide the diameters of the X axis and the Y axis in a cross section perpendicular to the axial direction at equal intervals. The cell wall thickness is one cell wall thickness, and the cell wall thickness is the average value t _av of the cell wall and the maximum value t of the cell wall thickness.
_{The max} and the minimum value t _min satisfy the relationship of t _av / (t _max −t _min ) ≦ 40. Where t _av / (t _max −t
The value of ( _min ) indicates the degree of variation with respect to the average value of the cell wall thickness, and the variation of the cell wall thickness is t
_By setting the value of _av / (t _max −t _min ) to be 40 or less, the cell wall thickness in the honeycomb structure is not uniform, so that there is no continuous cell wall intersection having so-called similar strength. Therefore, it is possible to prevent the phenomenon that cracks develop in a chain at the cell wall intersections due to thermal shock or thermal stress and break in the diagonal direction of the cell,
As a result, excellent thermal shock resistance characteristics can be obtained. On the other _hand, if the value of _{t a v / (t max -t} min) is more than 40, since the cell wall thickness of the honeycomb structure difference is reduced, since the strength of the cell wall intersections converges to the same extent The reason for this is that thermal shock and thermal stress cause a chain of cracks to develop at the intersections of the cell walls, which makes it easier to break in the diagonal direction of the cell, and the thermal shock resistance deteriorates. t _av / (t _max
The value of −t _min ) is preferably 1 to 40, more preferably 2 to 30. Where t _av / (t _max
The preferable range of the value of −t _min ) is set to 1 or more is that
If it is less than 1, the difference between the minimum wall thickness and the maximum wall thickness becomes large. Therefore, during extrusion molding of a honeycomb structure, the velocity balance of the clay clay of the ceramic raw material discharged from the slit portion of the known extrusion die. May deteriorate and the molded article may be bent or cracked, which is not preferable. By forming a curved portion as shown in FIG. 2 (c) at the intersection of the cell walls, the stress concentration factor at the intersection of the cell walls can be reduced, so that the strength at the intersection of the cell walls is improved and cracks are generated. It is possible to further prevent the phenomenon that the cells are broken in the diagonal direction. As the ceramic material constituting the ceramic honeycomb structure of the present invention, the present invention is mainly used as a carrier for a catalyst for purifying exhaust gas of an automobile engine or as a filter for removing fine particles in exhaust gas of a diesel engine. Since it is used, it is preferable to use a material having excellent heat resistance, cordierite, alumina,
It is preferable to use a ceramic material containing at least one selected from the group consisting of mullite, silicon nitride, silicon carbide and LAS as a main crystal. Among them, the ceramic honeycomb structure having cordierite as a main crystal is most preferable because it is inexpensive, has excellent heat resistance and chemical resistance, and has low thermal expansion.

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[0007]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be described in detail based on Examples.

Example 1 A ceramic honeycomb structure of the present invention comprises a cordierite forming raw material powder such as kaolin, calcined kaolin, alumina, aluminum hydroxide, silica and talc.
It is prepared as a raw material by mixing so as to have a cordierite composition. To this, a binder, a molding aid such as a lubricant, and if necessary, a pore-forming agent is added and mixed, and then water is added and kneaded,
A plasticizable batch was prepared and a honeycomb molded body was obtained by extrusion molding. At this time, the molding groove width on the outlet side of a known extrusion molding die is adjusted so that the cell wall thickness of the honeycomb structure becomes non-uniform, and a molded body having a cell wall as shown in FIG. 2 is obtained. did. Then, 140
Firing was performed at 0 ° C. to obtain a cordierite ceramic honeycomb structure 10 shown in FIG. The dimensions of the honeycomb structure were an outer diameter of 267 mm, a length of 300 mm, a cell wall average thickness of 0.3 mm, and a cell number of 46.5 cells / cm ² . The honeycomb structure has a porosity of 65% and an average pore diameter of 20.
was μm. The thickness of the cell wall of the obtained honeycomb structure was measured by the following method. As shown in FIG. 5 (a), the X-axis and Y-axis diameters 14 and 13 of the honeycomb structure are obtained.
The thickness 15 of the four cell walls surrounding the cells was measured for a total of 25 cells at 5 locations × 5 locations at which the cells were divided at equal intervals. The measurement was performed using a projector with a magnification of 100, and as shown in FIG.
The cell wall thickness 15 at the intermediate point was measured and taken as the cell wall thickness. Thus four locations / 1 cell × 25 places were measured, the measured value of the cell wall thickness of a total of 100 points, the average value _{t av,} the maximum value _{t ma x} and minimum value _{t min} from _{t av}
The value of / (t _max −t _min ) was determined. The thermal shock resistance of the obtained ceramic honeycomb structure was evaluated. The thermal shock resistance evaluation test was conducted by inserting the ceramic honeycomb structure into an electric furnace heated to a constant temperature, holding it for 30 minutes, then rapidly cooling it to room temperature, and then visually observing the temperature difference (heating temperature -Room temperature) was defined as the thermal shock resistance temperature. If no crack was found by visual inspection, the temperature was raised to 25 ° C. and the same test was performed, and the test was repeated until a crack was generated. The number of tests was three, and the average was shown. The results are shown in Table 1. Table 1
As shown in, the cell wall thickness is not uniform in the honeycomb structure _{t av / (t max -t min} ) value 40 following tests NO. 1 to 5 and test NO. The honeycomb structure of Nos. 8 to 9 has a problem in that the thermal shock resistance is used when used as a carrier for a catalyst for purifying exhaust gas of an automobile engine or as a filter for removing fine particles in exhaust gas of a diesel engine. There is no level of thermal shock resistance 70
The temperature was 0 ° C or higher. For this reason, there is little concern that cracks may occur due to thermal shock during actual use, leading to destruction. on the other hand,
Test No. in which the value of t _av / (t _max −t _min ) exceeds 40. In the honeycomb structures of Nos. 6, 7 and 9, the difference in cell wall thickness is small and uniform, so that the thermal shock resistance temperature is less than 700 ° C., and cracks occur due to thermal shock during actual use and break. I'm worried.

Front page continuation (51) Int.Cl. ⁷ Identification code FI theme code (reference) // B28B 3/26 ZAB B01D 53/36 C 4G069 F term (reference) 3G090 AA02 AA03 CA04 3G091 AA02 AB01 BA10 BA39 GA06 GA11 GB17X 4D019 AA01 BA05 BB06 BC07 BD10 CA01 4D048 BA10X BB02 BB15 EA06 4G054 AA05 AB09 AC00 BD19 4G069 AA08 AA10 BA13A BA13B CA03 DA06 EA19 EA25 ED06 FA01 FB67

Claims (2)

[Claims] 1. A ceramic honeycomb structure having an outer peripheral wall and a large number of cells surrounded by cell walls on the inner peripheral side of the outer peripheral wall, wherein the cell wall thickness is uniform in at least some of the cells. A ceramic honeycomb structure characterized by not being. 2. In a ceramic honeycomb structure having an outer peripheral wall and a large number of cells surrounded by cell walls on the inner peripheral side of the outer peripheral wall, the average value t _av of the cell wall thickness and the maximum value of the cell wall thickness are increased. The value t _max and the minimum value t _min satisfy the relationship of t _av / (t _max −t _min ) ≦ 40.